Electrosurgical instruments are known in the art and are used for electrosurgery. Typically, a suitable electrical generator provides a high frequency or radio frequency signal which is transmitted to a small surgical electrode having a thin knife-like tip which is applied to a patient. The patient is grounded to a patient plate, with the plate being connected by a further conductor back to the generator. The relatively small area of contact by the electrode with the patient provides an intense current in a highly localized area, producing a cutting action. The current then passes through the patient's body at the patient plate wherein the area of contact is large enough that no burning occurs at this location.
For cutting purposes, the generator is activated to produce a continuous signal, typically a sine wave signal. However, the same instrument may also be applied to the wound after cutting in order to produce coagulation. This coagulation is produced by a pulsing signal from the generator. Switching means are thus needed for the operator to switch between the two types of electrical energy produced by the generator.
Although a number of arrangements have been devised for selectively activating the electrical energy, the most satisfactory of these arrangements is a multiple wire cable conductor extending from the generator to the electrode. One conductor is normally connected to the electrode and two other conductors are selectively connectable to the therapeutic current conductor through switches to complete circuits back to the activating means for causing the generator to produce the desired mode of current.
Electrosurgical instruments found to be particularly safe and effective for surgical applications are those which incorporate finger activated switches, those which allow for readily interchangeable electrodes, those which are water resistant, and those which are thin and properly balanced for close surgical use where a certain feel is necessary. Such instruments are typically described as an electrosurgical pencil. However, such prior instruments have had many disadvantages in that the electrode connections were expensive to achieve, failed to provide a positive connection, and/or were subject to wear problems.
Disclosed in U.S. Pat. No. 4,032,738 (Esty et al.) is an electrosurgical instrument providing dome switches on the handle of the instrument to allow manual selection of cutting or coagulation signals from an electrosurgical generator. The instrument is generally flat to retain the feel of a nonelectrical surgical instrument.
U.S. Pat. No. 4,034,761 (Prater) discloses a disposable electrosurgical unit for applying either cutting signals or coagulation signals by the actuation of a switch in the handle of the unit. In particular, operation of the switch deforms a resilient conducting member which is electrically connected to the electrode blade, such that pushing the switch in one direction connects the resilient member to one electrosurgical energy source, and pushing the switch in the other direction connects the resilient member to another energy source, thereby conducting the selected electrosurgical energy to the patient.
U.S. Pat. No. 4,427,006 (Nottke) discloses an electrosurgical instrument providing an advantageous interface between an electrosurgical electrode and an electrosurgical generator. In particular, the wires of the cable are supported on a flat insert, and control pins are forced through the insulation of these wires. A conductor plate with cantilevered conductor strips lies over the insert and these strips are selectively connected to the contact pins by use of dome spring push buttons.
U.S. Pat. No. 4,625,723 (Altnether et al.) discloses an electrosurgical instrument including complex push button switches used to selectively bridge electrically isolated circuit contacts to apply either cutting or coagulation signals to a patient.
Other U.S. patents of general interest disclosing electrosurgical instruments include the following: U.S. Pat. No. 4,619,258 (Poole), U.S. Pat. No. 4,872,254 (Duliveria et al.), U.S. Pat. No. 4,492,832 (Taylor), U.S. Pat. No. 4,922,903 (Welch et al.), and U.S. Pat. No. 4,911,159 (Johnson et al.).